Top Environmental Fate Ecotoxicology Human Health Translations
Home
A to Z: All
A to Z: Insecticides
A to Z: Herbicides
A to Z: Fungicides
A to Z: Other product constituents
Search
Support information
Purchasing and licensing
Imazapyr
Last updated: 27/11/2019
(Also known as: imazapyr acid)

GENERAL INFORMATION
Description
A herbicide for non-crop land applications which is particularly effective on hard-to-control perennial grasses
Example pests controlled
Annual and perennial grasses, Broad-leaved weeds; Woody plants; Brambles; Brush
Example applications
Forestry; Wetland sites; Non-cropped areas
Efficacy & activity
-
Availability status
Current
Introduction & key dates
1985
UK regulatory status
UK approval status
Not approved
EC Regulation 1107/2009 (repealing 91/414)
EC Directive 91/414 Status
Not approved
Dossier rapporteur/co-rapporteur
-
Date inclusion expires
Expired
EU Candidate for substitution (CfS)
-
Listed in EU database
Yes
Approved for use (✓) or known to be used (#) in the following EU-27 Member States
ATAustria
BEBelgium
BGBulgaria
CYCyprus
CZCzech Republic
DEGermany
DKDenmark
EEEstonia
ELGreece
                 
ESSpain
FIFinland
FRFrance
HRCroatia
HUHungary
IEIreland
ITItaly
LTLithuania
LULuxembourg
                 
LVLatvia
MTMalta
NLNetherlands
PLPoland
PTPortugal
RORomania
SESweden
SISlovenia
SKSlovakia
                 
Also used in
Also used in
Australia, USA
Chemical structure
Isomerism
A chiral molecule existing in the S- and R-forms
Chemical formula
C₁₃H₁₅N₃O₃
Canonical SMILES
CC(C)C1(C(=O)NC(=N1)C2=C(C=CC=N2)C(=O)O)C
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
CLQMBPJKHLGMQK-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/C13H15N3O3/c1-7(2)13(3)12(19)15-10(16-13)9-8(11(17)18)5-4-6-14-9/h4-7H,1-3H3,(H,17,18)(H,15,16,19)
2D structure diagram/image available?
Yes
General status
Pesticide type
Herbicide
Substance group
Imidazolinone
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Non-selective, absorbed by foliage and rapidly translocated. Controls vegetation by interfering with an enzyme pathway. Inhibits plant amino acid synthesis - acetohydroxyacid synthase AHAS.
CAS RN
81334-34-1
EC number
-
CIPAC number
530
US EPA chemical code
128821
PubChem CID
54738
Molecular mass
261.28
PIN (Preferred Identification Name)
-
IUPAC name
2-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]nicotinic acid
CAS name
2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl)-3-pyridinecarboxylic acid
Other status information
-
Relevant Environmental Water Quality Standards
-
Herbicide Resistance Classification (HRAC)
B
Herbicide Resistance Classification (WSSA)
2
Insecticide Resistance Classification (IRAC)
Not applicable
Fungicide Resistance Classification (FRAC)
Not applicable
Examples of recorded resistance
Lolium rigidum
Physical state
Off-white to tan coloured solid
Formulations
Property
Value
Example manufacturers & suppliers of products using this active now or historically
  • Arsenal
  • Chopper
  • Habitat
  • Stalker
  • Katrin
  • Katrin Forestal
Example products using this active
  • Nomix-Chipman
  • BASF
  • Makhteshim Agan Group
UK LERAP status
No UK approval for use as a pesticide under EC Regulation 1107/2009
Formulation and application details
Usually supplied as an aqueous solution that contains a wetting agent
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
9740
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
33900
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Acetone
-
9.5
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Hexane
-
105000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Methanol
-
1800
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Toluene
-
Melting point (°C)
171
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
Boiling point (°C)
- - -
Degradation point (°C)
- - -
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
1.29 X 1000 Calculated -
Log P
0.11
H4 H = The US ARS pesticide properties database (click here )
4 = Verified data
Low
Bulk density (g ml⁻¹)
1.34
Q2 Q = Miscellaneous internet resources
2 = Unverified data of unknown source
-
Dissociation constant pKa) at 25 °C
1.9
DW4 DW = Don Wauchope personal database for Pka data: Wauchope, R. D. and Edwards, J. Dissociation constants for pesticide active ingredients: a database and comparison with predicted values. MS in preparation
4 = Verified data
-
pKa(2) 3.6, pKa(3) 11.0
Vapour pressure at 20 °C
0.013
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Low volatility
Henry's law constant at 25 °C
3.00 X 10-07
H4 H = The US ARS pesticide properties database (click here )
4 = Verified data
Non-volatile
GUS leaching potential index
1.98 Calculated Transition state
SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate
Value
4.02 X 10-02 Calculated -
Note
-
Potential for particle bound transport index
Low Calculated -
Maximum UV-vis absorption L mol⁻¹ cm⁻¹
- - -
Surface tension (mN m⁻¹)
- - -
Degradation
Property
Value
Source; quality score; and other information
Interpretation
General biodegradability
-
Soil degradation (days) (aerobic)
DT₅₀ (typical)
11
A5 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications )
5 = Verified data used for regulatory purposes
Non-persistent
DT₅₀ (lab at 20 °C)
11
A5 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications )
5 = Verified data used for regulatory purposes
Non-persistent
DT₅₀ (field)
- - -
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
DT₅₀ modelling endpoint
- - -
Note
EU dossier lab studies DT₅₀ range 5.9-16.5 days; Other sources: DT₅₀ 90 days (DW4), 25-142 (F3)
Dissipation rate RL₅₀ on plant matrix
Value
- - -
Note
-
Dissipation rate RL₅₀ on and in plant matrix
Value
26.0
R3 R = Peer reviewed scientific publications
3 = Unverified data of known source
-
Note
Forest plant leaves, n=1
Aqueous photolysis DT₅₀ (days) at pH 7
Value
2.1
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderately fast
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
30
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderately persistent
Note
-
Water-sediment DT₅₀ (days)
- - -
Water phase only DT₅₀ (days)
- - -
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd
- - -
Koc
-
Notes and range
-
Freundlich
Kf
1.23
A5 A = EU regulatory and evaluation data as published by EC, EFSA (RAR, DAR & Conclusion dossiers), EMA (e.g. EU Annex III PIC DGD) (EU - Pesticides database; EFSA Scientific Publications )
5 = Verified data used for regulatory purposes
Moderately mobile
Kfoc
125
1/n
0.94
Notes and range
EU dossier Kf range 0.64-1.81; 1/n range 0.90-0.97; Other literature data Kf range 0.84-33,24 mL g⁻¹, Kfoc range 17.9-3022 mL.g, 1.n range 0.50-0.81, Soils=6 (R4)
pH sensitivity
-
ECOTOXICOLOGY
Property
Value
Source; quality score; and other information
Interpretation
Bio-concentration factor
BCF (l kg⁻¹)
2.54
Q2 Q = Miscellaneous internet resources
2 = Unverified data of unknown source
Estimated
Low potential
CT₅₀ (days)
Not available -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
> 2000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
Low
Mammals - Short term dietary NOEL
(mg kg⁻¹)
-
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
-
(ppm diet)
10000 -
Birds - Acute LD₅₀ (mg kg⁻¹)
2150
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Anas platyrhynchos
Low
Birds - Short term dietary (LC₅₀/LD₅₀)
- - -
Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
> 100
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Oncorhynchus mykiss
Low
Fish - Chronic 21 day NOEC (mg l⁻¹)
43.1
P4 P = Other governments and regulators
4 = Verified data
Oncorhynchus mykiss 28 day
Low
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
> 100
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Daphnia magna
Low
Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)
> 97.1
P3 P = Other governments and regulators
3 = Unverified data of known source
Daphnia magna
Low
Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)
- - -
Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)
- - -
Aquatic plants - Acute 7 day EC₅₀, biomass (mg l⁻¹)
0.024
F3 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents (US EPA Databases Related to Pesticide Risk Assessment )
3 = Unverified data of known source
Lemna gibba
Moderate
Non-target plants
- - -
- - -
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
71
W2 W = French database provided by ARVALIS-Institut du Végétal
2 = Unverified data of unknown source
Unknown species
Low
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
- - -
Honeybees (Apis spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
> 100
F4 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents (US EPA Databases Related to Pesticide Risk Assessment )
4 = Verified data
Apis mellifera
Low
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
25
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderate
Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Bumblebees (Bombus spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
-
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
-
Mason bees (Osmia spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Other pollinators (1)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Other pollinators (2)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)
133
K4 K = Research datasets, e.g. Pandora, Demetra
4 = Verified data
Moderate
Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)
- - -
Other soil macro-organisms
Acute LC₅₀ (mg kg⁻¹)
- - -
Chronic NOEC (mg kg⁻¹)
- - -
Other arthropod (1)
LR₅₀ g ha⁻¹
- - -
% Effect
- - -
Other arthropod (2)
LR₅₀ g ha⁻¹
- - -
% Effect
- - -
Soil micro-organisms
- - -
Mesocosm study data
NOEAEC mg l⁻¹
- - -
NOEAEC mg l⁻¹
- - -
HUMAN HEALTH AND PROTECTION
General
Property
Value
Source; quality score; and other information
Interpretation
Threshold of Toxicological Concern (Cramer Class)
High (class III) - -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
> 2000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
Low
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
2000
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
-
Mammals - Inhalation LC₅₀ (mg l⁻¹)
5.1
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Rat
-
Other Mammal toxicity endpoints
- - -
ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)
- - -
ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)
- - -
AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)
- - -
AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)
- - -
Dermal penetration studies (%)
- - -
Dangerous Substances Directive 76/464
- - -
Exposure Routes
Public
-
Occupational
-
European MRLs
EU MRL pesticide database 
Drinking Water Standards
- - -
Drinking Water MAC (μg l⁻¹)
- - -
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
XNo, known not to cause a problem
A0 A = Chromosome aberration (EFSA database)
0 = No data
;
B0 B = DNA damage/repair (EFSA database)
0 = No data
;
C0 C = Gene mutation (EFSA database)
0 = No data
;
D0 D = Genome mutation (EFSA database)
0 = No data
;
E0 E = Unspecified genotoxicity type (miscellaneous data source)
0 = No data
No data found
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
XNo, known not to cause a problem
XNo, known not to cause a problem
XNo, known not to cause a problem
Respiratory tract irritant Skin irritant Skin sensitiser
Yes, known to cause a problem
Yes, known to cause a problem
No data found
Eye irritant Phototoxicant  
Yes, known to cause a problem
No data found  
General human health issues
Highly toxic
Handling issues
Property
Value and interpretation
General
Prevent generation of mists
CLP classification 2013
Health: H319
Environment: H412
EC Risk Classification
Xi - Irritant: R36
N - Dangerous for the environment: R52, R53
EC Safety Classification
S2, S26, S61
WHO Classification
U (Unlikely to present an acute hazard)
UN Number
-
Waste disposal & packaging
-
TRANSLATIONS
Language
Name
English
imazapyr
French
imazapyr
German
Imazapyr
Danish
imazapyr
Italian
imazapir
Spanish
imazapir
Greek
imazapyr
Polish
imazapyr
Swedish
imazapyr
Hungarian
-
Dutch
imazapyr

Record last updated: 27/11/2019
Contact: aeru@herts.ac.uk
Please cite as: Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242